Hi, I understand what you mean by not remembering the last time you were truly happy.
I'm also 17 so I don't have too much life experience but there's been times when I've become better on my own. However, those issues were related to seasonal depression which is fairly normal and it wasn't a big deal to me.

I had what I think was symptoms of mild psychosis about 2 years ago and I went to therapy and I was prescribed medication to prevent further depression.
I was better for a while and I thought I had my life together but now everything is coming back and I've recently started going to a therapist again.

My advice is to get help with your anorexia and maybe see a therapist about your sadness and anger issues.
For me it got worse the longer I waited.